C++ : Java Glossary

2008-01-04 by Roedy Green ©1996-2008 Canadian Mind Products
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C++

The forefather of Java. You can call C++ routines from Java via native method calls. I learned C++ before Java. Much of my trouble at the beginning came from presuming they worked the same way just because they look similar.

Differences	C/C++ Header Libraries
Microsoft C++ Keywords	Books
Microsoft C++ sizeof	Links

Differences between C++ and Java

The major differences between C++ and Java are:

An array of objects in C++ is a typically a set of structs packed one right after the other in RAM. In Java, it is an array of pointers (aka references). The pointers each point to an Object floating independently out there on the heap somewhere.
In Java, the sizes of int, long etc. are rigidly defined in terms of bits. In C++ they are platform-dependent.
In Java, the JVM behaves at if it were big endian, even if internally it is actually little-endian. In C++, the endianness is platform dependent.
In Java, the choice of stack of heap allocation is handled automatically by the compiler (Sun’s javac is not very bright always using the heap for objects, and the stack for local primitives and references) and garbage collection of unreferenced objects is automatic. In C++, you have manual control over where objects are created. The lifetime of objects created on the stack is automatically controlled, deallocation and destructor automatically called when the method exits; this is known as deterministic destruction. Whereas you have to manually control the lifetime of dynamic objects allocated with new by invoking the destructor.
In Java you don’t know for sure that all finalizers will be run; in C++ you do, because you invoke the destruciors manually. You could write manually invoked destructors in Java, but they would still not immediately recover the RAM.
In Java, references are constrained to point only to the beginnings of objects. You cannot do any form of arithmetic on them. All you can do is compare them for equality. In C++, you can do arithmetic on pointers and make pointers point anywhere in the address space. In Java, there is only one way to address an object, via a reference which always points to the start of the object (or more precisely to the start of the roughly 16 bytes of housekeeping fields preceding an object). In C++ there are many ways to address an object, including directly, via pointer arithmetic into the middle of the object, via pointer, via address. In Java there is one addressing operator .. In C++, you use . & * -> [].
In Java, you cannot overload operators. In C++, you can.
In Java, by default methods are virtual (overrideable). In C++, by default, methods are non-virtual.
Java object code (class files containing JVM byte codes) will run unmodified on any platform that supports the JVM. C++ object code must be first linked to produce an executable containing platform-specific machine instructions. It will run only on one platform.
Java checks all subscripts that they are in bounds and all casts for validity. C++ does not.
Java requires a JVM to execute. C++ programs are usually freestanding.
Java does not use a preprocessor. C makes extensive use of a macro preprocessor. C++ tends to use inline functions with less use of the macro preprocessor.
Java does not allow multiple inheritance, though a class may implement several interfaces. C++ supports multiple inheritance.
Java generics are a purely compile time type checking mechanism with type erasure at run time. C++ generics are templates, more like macro expansions of the code for each type.
Java has built-in threads and synchronization. C++ relies on platform-specific user-written thread libraries.
Java has a vast standard library set, including AWT and Swing. C++ has a relatively modest standard set of methods, and relies on platform-specific GUI libraries.
Java does not let you embed assembler or platform-dependent code. C++ lets you embed machine code assembler and have full access to the native platform API.
In Java, only one type of data can be stored in any variable. In C++, you can have unions where alternate types of data are stored in the same slot in a struct.
In Java, all classes derive from Object. In C++, classes have no common base.
In Java, all method and field definitions must be inside some class. In C++, you can also define functions and variables independently of classes (and in fact, you don’t need to define any classes at all to write a C++ program).
Java is defined by Sun. C++ is defined by an ISO standard.
Java has the final keyword and C++ has const. C++ gives you finer control, but that control can be overridden with a cast.
Using JNI, Java can call C++/C methods and vice versa.

Learning Java is much like learning a foreign language. The sooner you start learning to think in the language, rather than think in your native language (C++) and translating, the better command of the language you develop. This is even truer of Java than most other computer languages because Java is so strongly idiomatic. There are canned ways of doing almost everything. You build very little from scratch from the primitive elements.

Java superficially looks a lot like C++, but nearly all my trouble learning Java came from presuming it should work the same as C++ or should have buried somewhere some feature I used in C++. It works quite differently inside and has a completely different design philosophy. The rule of thumb is, don’t presume Java works the same as C++ just because the syntax looks the same. Java is a bit like an angler fish that dangles a C++ syntax lure to seduce C++ programmers into trying Java (for their own good, of course).

Microsoft C++ Keywords

Microsoft C++ Keywords
__abstract	__int	__try_cast	delete	goto	property	true
__alignof	__int6	__unaligned	deprecated	if	protected	try
__asm	__int64	__unhook	dllexport	in	public	typedef
__assume	__int8	__uuidof	dllimport	initonly	ref	typeid
__based	__interface	__value	do	inline	register	typename
__box	__leave	__virtual_inheritance	double	int	reinterpret_cast	union
__cdecl	__m64	__w64	dynamic_cast	interface	return	unsigned
__declspec	__m8	__wchar_t	each	interior_ptr	safecast	using
__delegate	__m8d	abstract	else	literal	sealed	uuid
__event	__m8i	array	enum	long	selectany	value
__except	__multiple_inheritance	bool	event	mutable	short	virtual
__fastcall	__nogc	break	explicit	naked	signed	void
__finally	__noop	case	extern	namespace	sizeof	volatile
__finally	__pin	catch	false	new	static	wchar_t
__forceinline	__property	char	finally	noinline	static_cast	while
__gc	__raise	class	float	noreturn	struct
__hook	__sealed	const	for	nothrow	switch
__identifier	__single_inheritance	const_cast	friend	novtable	template
__if_exists	__stdcall	continue	friend_as	nullptr	this
__if_not_exists	__super	default	gcnew	operator	thread
__inline	__try	delegate	generic	private	throw

Microsoft C++ sizeof

The sizes of various data types is platform dependent in C++, however here is what they mean when developing for Microsoft Windows Vista C++.

sizeof various data types is Microsoft C++ for Windows Vista
C++ Type	Closest Java Type	Bytes	Bits	Notes
boolean	boolean	1	8	1-byte boolean, defined as unsigned char.
BOOLEAN	boolean	1	8	1-byte boolean
byte	byte	1	8	unsigned
BYTE	byte	1	8	unsigned
char	byte	1	8	8-bit signed chars.
unsigned char	byte	1	8	8-bit unsigned chars.
TCHAR	char	2	16	Unicode 16-bit chars. On older systems compiles to 8-bit.
wchar_t	char	2	16	Unicode 16-bit unsigned chars
WCHAR	char	2	16	Unicode 16-bit unsigned chars
short	short	2	16	signed
USHORT	char	2	16	unsigned
int	int	4	32	signed
size_t	int	4	32	unsigned
BOOL	boolean	4	32	4-byte boolean
long	int	4	32	signed
DWORD	int	4	32	unsigned
void*	Object	4	32	Pointer/Reference
float	float	4	32	IEEE float
long long	long	8	64	signed
double	double	8	64	IEEE double

See also the table of JNI types. I discovered the information for the above table by running the following C++ program. You can modify it to prepare a list of types and sizes for your C/C++ projects.

C/C++ Header Libraries

To use a C/C++ method you need include its prototype in a header file. Here are some of the most common header files and what the rougly contain:

Common C/C++ header files
Header	Contents
afx.h	includes Windows API and common C headers too.
afxcmn.h	MFC support for Windows Common Controls
afxdtctl.h	MFC support for Internet Explorer 4 Common Controls
afxext.h	MFC extensions
afxwin.h	MFC core and standard components
assert.h	assert
conio.h	getch, putch
ctype.h	isUpper, isLower, toUpper
direct.h	chdir, mkdir
dos.h	DOS API
fcntl.h	open flags: O_RDONLY, _O_CREAT, _O_EXCL
io.h	_chsize, _chmod, _lseek
jni.h	Java JNI library
mmsystem.h	playsound
process.h	exec, spawn
resource.h	generated to include resources
share.h	sharing flags: _SH_DENYRW, _SH_DENYWR, _SH_DENYRD, _SH_DENYNO, _SH_SECURE
stdafx.h	standard precompiled header
stdio.h	fclose, fgetc, printf, remove, rename, setvbuf
stdlib.h	exit, putenv, splitpath
string.h	strcpy, strcat, strcmp, strupr
sys\stat.h	read/write permissions: _S_IREAD, _S_IWRITE
tchar.h	16-bit chars, TCHAR
winbase.h	time structures: _FILETIME, _SYSTEMTIME
windows.h	Windows API

Books

recommend book⇒C++ For Java Programmers

paperback

ISBN13:

978-0-201-61246-2

ISBN10:

0-201-61246-1

publisher:

Addison Wesley

published:

1999-04-02

by:

Timothy A. Budd

This is the same title as Mark Weiss’s book. Note the direction. Most books presume you know C++ and need to learn Java. This one presumes you know Java and need to learn or brush up on C++ for doing JNI or related work.

	amazon.ca	amazon.com
	chapters.indigo.ca	powells.com
	amazon.fr	barnesandnoble.com
	amazon.de	amazon.co.uk

recommend book⇒C++ For Java Programmers

hardcover

ISBN13:

978-0-13-919424-5

ISBN10:

0-13-919424-X

publisher:

Prentice Hall

published:

2003-11-07

by:

Timothy A. Budd

This is the same title as Timothy Budd’s book. Note the direction. Most books presume you know C++ and need to learn Java. This one presumes you know Java and need to learn or brush up on C++ for doing JNI or related work.

	amazon.ca	amazon.com
	chapters.indigo.ca	powells.com
	amazon.fr	barnesandnoble.com
	amazon.de	amazon.co.uk

recommend book⇒Beginning Visual C++ 6

paperback

ISBN13:

978-1-86100-088-0

ISBN10:

1-86100-088-X

publisher:

Wrox Press

published:

1998-08

by:

Ivor Horton

A gentle, easy-paced introduction to C++.

	amazon.ca	amazon.com
	chapters.indigo.ca	powells.com
	amazon.fr	barnesandnoble.com
	amazon.de	amazon.co.uk

recommend book⇒Accelerated C++: Practical Programming by Example

paperback

ISBN13:

978-0-201-70353-5

ISBN10:

0-201-70353-X

publisher:

Addison-Wesley

published:

2000-08-24

by:

Andrew Koenig, Barbara E. Moo

Recommended for people who know Java and want to learn C++.

	amazon.ca	amazon.com
	chapters.indigo.ca	powells.com
	amazon.fr	barnesandnoble.com
	amazon.de	amazon.co.uk

recommend book⇒The Design and Evolution of C++

paperback

ISBN13:

978-0-201-54330-8

ISBN10:

0-201-54330-3

publisher:

Addison-Wesley

published:

1994-04-08

by:

Bjarne Stroustrup

This is a fascinating book about the birth of a new computer language C++. He talks about the politics, the compromises, and the factors that made him design C++ the way it is.

	amazon.ca	amazon.com
	chapters.indigo.ca	powells.com
	amazon.fr	barnesandnoble.com
	amazon.de	amazon.co.uk

recommend book⇒The C++ Programming Language (3rd Edition)

paperback

hardcover

ISBN13:

978-0-201-88954-3

978-0-201-70073-2

ISBN10:

0-201-88954-4

0-201-70073-5

publisher:

Addison-Wesley

published:

1997-06-30

by:

Bjarne Stroustrup

A reference manual for C++, rather formal.

	amazon.ca	amazon.com
	chapters.indigo.ca	powells.com
	amazon.fr	barnesandnoble.com
	amazon.de	amazon.co.uk

recommend book⇒The Annotated C++ Reference Manual

paperback

ISBN13:

978-0-201-51459-9

ISBN10:

0-201-51459-1

publisher:

Addison-Wesley

published:

1990-01-11

by:

Margaret A. Ellis, Bjarne Stroustrup

A book for language lawyers on the fine points of C++. It is not suitable for initially learning the language. It is really more aimed at compiler writers. It covers C++ implementation techniques including vtbls.

	amazon.ca	amazon.com
	chapters.indigo.ca	powells.com
	amazon.fr	barnesandnoble.com
	amazon.de	amazon.co.uk

recommend book⇒Java Programming: Making the Move from C++

paperback

ISBN13:

978-1-85032-922-0

ISBN10:

1-85032-922-2

publisher:

International Thomson Computer Press

published:

1998-07-21

by:

Joe Wigglesworth and Paula Lumby

Does not discuss anything past Java 1.1.

	amazon.ca	amazon.com
	chapters.indigo.ca	powells.com
	amazon.fr	barnesandnoble.com
	amazon.de	amazon.co.uk

C
const
final
garbage collection
Java
JNI
Table of JNI types

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